reset texture paint brushes?
The brush settings are loaded even if the Load UI option is disabled. The brush type can be adjusted in the brush menu, so if you have deleted the brush you can create a new brush and set it to smear.



You can import brushes from another file so to restore the default brushes without changing any of your other settings, choose File->Load Factory Settings, then save the blend file somewhere, then create a new file to get your normal settings back and import the brushes from the factory file you just saved and re-save your startup file.